The plans say to tap the hole in the F-712E tiedown bar. I went to the hardware store and found this 3/8 x 16 hand tap and 5/16 drill. After enlarging the hole to 5/16, I used the tap with lots of Boelube and cleared the treads every quarter turn. Next I riveted the tidown bar to the F-712 bulkhead per the plans.
